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Basic Flash Use

Lightning Bug flying out of Light Bulb

Flash is the most misused part of the camera. Unless you are a miner and are used to having a light attached to your head all day, the most unnatural way to light your subject is from the same angle or perspective you are viewing the subject. Unfortunately there really isn't a better place to put the flash on a camera. There are a number of ways to improve your flash photos. But first, it is best to learn everything you can about how your flash works.

Nobody likes flash in their eyes. Here are some of the problems we have to overcome with our flash:
  1. Foreground objects are bright while background objects are very dark
  2. Mixed lighting temperatures, room lights are yellow
  3. Washed out foreground
  4. Dark shadow around your subject
  5. Flat image without good shadow details
  6. Blinking, squinting, red eye, Nobody likes flash in their eyes

Flash Range Flash Range
Every flash has a maximum useful range. The intensity of the flash when it reaches a subject depends on the flash's power and on how far the light has to travel. The further the subject is from the flash, the less light will reach it and so the less light will be reflected from the subject back toward the camera.

When the flash fires, the beam of light expands as it moves further from the camera so its intensity falls off with distance. Reflected light from your subject continues to dispurse as it travels back to the camera. As a result, subjects nearer the flash will be illuminated with a more intense light than subjects farther away. The rate at which the light falls off is described by the inverse square law. The law states that if the distance between the flash and subject is doubled, only one quarter the amount of light will reach the subject because the same amount of light is spread over a larger area. Conversely, when the distance is halved, four times as much light falls on a given area.

Learn the limits of your flash. Take your camera outside and take some evening photos of a tree or car or building with your flash turned on. Walk away and take another shot. Examine the photo each time. This will help you learn how far away from your subject you can be before your flash is not effective. Do not use a subject that is promarily white. White will reflect all the light and give you better results but it will not be an acurate test since most of your subjects will not be white.

Flash Range Flash Range

These photos were taken from a great distance from the subject. In the first photo the camera is set on Auto mode which adjusts the shutter speed to 1/60th of a second. The flash is not strong enough to travel across the lake, light up the subject, then bounce back to expose the photo in the camera. In the second photo the flash is turned off forcing the camera to use a slow shutter speed to caputer ambient light. In this mode, a tripod must be used and the subject cannot be something that moves. These photos demonstrate how built in flash is not strong enough to light up subjects at a great distance. If your subject is far away, there are a few other flash setting choices available.

1/60th second rule
Did you ever notice that every time you turn your flash on the shutter speed goes to 1/60th of a second? When your camera is set to Automatic or Program mode the camera calculates the shutter speed and aperture for you. And when you turn on your flash the camera automatically sets the shutter speed to 1/60th of a second. Why does the camera do this? It's because of the basic shutter speed rule that you cannot hold your camera still enough for a sharp picture if the shutter speed drops below 1/60th of a second. This is the way the camera behaves in these basic camera modes. To use some of the more advanced flash options the camera needs to be in shutter priority mode (Tv or S depending on your camera model) or use slow-sync flash mode if your camera is equipped with it. These advanced settings are described in the slow-sync tutorial.

Now that we know why the camera cares about shutter speed when flash is turned on, why do we care? Lets take a look at that concert photo with the backs of the heads exposed perfectly while the stage is dark. We'll take this shot step by step. First note that the camera is in automatic mode. The room is dark so there is not enough light to get the shot with a shutter speed above 1/60th of a second. So the first thing the camera does is engages flash and sets the shutter speed to 1/60th of a second. Think about that for a moment. The room is too dark to get a proper exposure if we use a shutter speed 1/60th of a second or above but at the same time the camera is forcing the shutter speed to 1/60th of a second. What does that tell you? It tells me that if the flash doesn't fire everything in the photo will be very dark. That means we are depending on the flash alone to light up our subject. What happens next? The flash fires it's pre-flash which bounces off our subject then returns to the camera to calculate the flash setting for a proper exposure. What is the first thing the flash is going to bounce off of? The closest thing in the photo. In this case, the backs of the heads of the people sitting in front of you. Anything else in the photo that is further away will be dark. Another common example is a group of people sitting at a table. The people in front are exposed properly but the people in the back are dark.

The Light Race
Another problem with flash is the way it meter's the light bounced back from the subject. When the flash emits it's burst of light it races to the subject being photographed, bounces off and races back to the camera. The light that gets back first wins. What light will get back first? The light that bounces off the first object in the photo. Once this light reaches the camera, the light meter senses that enough light has returned and shuts down. This is especially a problem when the closest object is white. Flash intensity calculations are based on the first light that bounces back to the camera. This means that the closest subject will be exposed properly but anything further away will become darker and darker the further away it is.

Bounce Flash
A bounce flash gives you the option of pointing the flash up at the ceiling thus "bouncing" the light. This spreads the light out more evenly across your subject. It also eliminates red eye. This works well for the people sitting at the table. The concert photo is a bigger problem. There may not be a white ceiling to bounce the flash off. Also, the people may simply be too far away. In this case, you will have to get closer to your subject or try not to use flash at all.

Taking Control of Your Flash
Flash on
Flash off
This is a typical birthday party snapshot. The first mistake happens when you don't pay attention to everything in your photo. Background junk clutters the photo. The photo is taken while standing, looking down at the subject. It is best to get eye-level with your subject. The subject looks uncomfortable and posed dead center. Flash is turned on which causes an undesirable dark shadow around the subject. A bright sunbeam is over-exposing the hair. We can improve this shot in just a few steps.

The first thing I did was ask the subject to move about two feet to her left. Then I took two steps to my left and got on my knee. There was a white sweater flung over the back of a chair next to me. I asked my brother-in-law to hold it in the sunbeam which reflected the light back at the subject. Finally I turned off the flash. The difference was like night and day!

Coming soon

Fill Flash

Maximum Sync Speed

Red Eye

Flash intensitiy